The Static Performance And Seismic Response Analysis Of Cable-staved Bridge Without Backstays

With the constant improvement of the cable-stayed bridge design theory and the gradual promotion of the bridge aesthetics,designers break the structural style of conventional cable-stayed bridges by tilting the pylon and cancelling the backstays,forming a novel and powerful structure,namely,cable-stayed bridges without backstays.Its unique and charmful landscape still inject vitality to the development of this kind of bridges,although it is more difficult for cable-stayed bridges without backstays to be designed and constructed than traditional cable-stayed bridges.The application of it started relatively late and just a small amount of those bridges had been built in China,meanwhile,the background bridge in this paper,ShouChun west road bridge,was a “V” type and two-way tilting cable-stayed bridge without backstays which was firstly adopted domestically,so it has great directive and realistic significance to analyze the static performance and seismic response of this kind of bridges.The main contents and achievements are as follows:(1)This paper sketched the development of cable-stayed bridges without backstays,summarized the research status of the static performance and seismic response at home and abroad and pointed out the purpose and significance of this research.(2)This paper discussed the structural system and characteristics of the static equilibrium based on cable-stayed bridges without backstays which had been built at home and abroad and summarized the structural features of ShouChun west road bridge.(3)A spatial finite element model was established by Midas Civil on the background of this bridge.This paper also studied the structural features of this bridge subjected to dead load and the changing laws of inner forces and deformation by the changes of structural parameters.It turned out that,the longitudinal and lateral deformations of the main pylon under dead load were broadly apparent,the weight of the main and accessory pylon and the initial tension of cables exerted tremendous influences on the longitudinal deformation and the bending moment at the end of the accessory pylon.(4)The dynamic characteristics of the bridge were analyzed.This paper also studied the influences of different anchor positions and the arrangement of a transverse beam between two main pylon columns on the dynamic characteristics.It showed that,the first mode of vibration was longitudinal bending of the main pylon,thus,the vibration of it was prominent.It was conducive to adding the longitudinal stiffness to the accessory pylon by anchoring the cables of the main pylon in the accessory pylon.Meanwhile,the integral rigidity was increased due to the arrangement of the transverse beam.(5)Seismic response of the bridge was analyzed and compared using the response spectrum method and time history method.It turned out that,the influence of the longitudinal seismic load was apparent,at the same time,the internal forces reached its peak value at the cross section of the main girder.The most important positions which should be focused on during the design of the seismic resistance were the bottom of the piers,the consolidations between the pylons and girder,the main girder between two consolidations.(6)The influence of damping parameters of viscous dampers on the seismic response of the bridge was carried out.The damping parameters were optimized by the fitting functions of response values and the nonliear function optimization method in Matlab.The settings of viscous dampers which had been optimized could significantly reduce the deformation of the structure and improve its force performance of key positions under the seismic load,with the lower cost of viscous dampers.